Co-production of electricity, heat and biocoal pellets from biomass: a techno-economic comparison with wood pelletizing Berit Erlach * , Benjamin Wirth, George Tsatsaronis Technische Universität Berlin, Institute for Energy Engineering, Berlin, Germany * Corresponding author. Tel: +49 30 31428449, Fax: +49 30 31428613, E-mail: erlach@iet.tu-berlin.de Abstract: Hydrothermal carbonization (HTC) is an artificial coalification process which converts raw biomass into a coal-like product, biocoal. Biocoal has a higher energy density than the original biomass and is easier to transport, store and process. Hence, HTC is recently promoted as an upgrading technology, especially for wet biomass. For HTC to become a commercial technology, it is essential to identify applications which offer technical or economic advantages over conventional biomass processes. This paper presents a process design where HTC is integrated with wood-fired combined heat and power production (HTC-CHP), and compares it to standalone HTC (HTC-sep) and to wood pelletizing integrated with CHP (WP-CHP). The respective plant designs are modeled with Aspen Plus and an economic analysis is performed using investment costs from literature. The overall efficiency of electricity, heat and wood or biocoal pellet production is very close in all considered cases. When biodegradable waste is available at zero cost, the production costs of biocoal pellets are similar to those of wood pellets. If wood chips are used as an HTC feedstock, the production costs are 32–38% higher. The average cost of CO 2 avoidance is highest for the standalone HTC plant, due to the auxiliary consumption of natural gas and electricity. Keywords: hydrothermal carbonization, biocoal, biomass, wood pellets 1. Introduction Co-firing with coal has been identified as one of the least expensive and most efficient technologies for converting biomass to electricity [1]. This gives rise to a demand for biofuels with a uniform quality and high energy density, which can be processed in the fuel handling and combustion equipment of existing coal-fired power plants. Since most raw biomass falls short of these requirements, upgrading technologies, which improve the properties of biomass for transport, storage, combustion and gasification, have become of interest. The most established upgrading technology today is wood pelletizing, whereby wood is dried, milled and pressed into pellets of a defined form and size. Several technologies which convert biomass into a more coal-like product through chemical processing are currently being developed, but not yet commercialized. While torrefaction and fast pyrolysis have been mainly applied to dry wood and straw, hydrothermal carbonization (HTC) does not require prior drying and has been successfully tested with a wide range of biomass including wood, straw, cut grass, municipal waste, digestate, and bark mulch in laboratory scale experiments [2,3]. To achieve a high overall energetic efficiency of 80 to 90% (HHV basis), efficient heat recovery within an HTC plant is required [4]. However, complex heat recovery might not be attractive due to operability issues and cost. This paper presents a process design in which the need for a complex heat recovery design within the HTC process is eliminated by integrating the HTC process with wood-fired combined heat and power production (CHP). Steam for the HTC reactor is bled from a steam turbine extraction, while low temperature heat from the cooling of the HTC reaction products is used for district heating and for combustion air and water preheating for the CHP process. This integrated design is compared to a s tand-alone HTC plant and to wood pelletizing, also integrated with CHP, in relation to energetic efficiency and production costs. Poplar wood chips from short rotation coppice and biodegradable waste are considered as feedstocks for the HTC process. 508